Evidence for Extratumoural Storage of Catecholamines in Pheochromocytoma Patients

Abstract

Following the removal of a pheochromocytoma in three female patients the daily excretion of catecholamines and their metabolites was still considerably elevated for about one week. The excretion rates declined during this period with half-lives of 1.8 to 10.9 days for catecholamines and 2.1 to 4.7 days for metanephrines, vanilmandelic acid, and vanilglycol. The cumulative urinary excretion of catecholamines and their metabolites following surgical removal of the tumour was nearly as high as the catecholamine content of the pheochromocytomas. This large amount of catecholamines must have been located outside the tumour, most probably within the sympathetic nerve, where it is subject to release following physiological stimuli. Furthermore, this fact may provide an explanation for hypertensive crises in pheochromocytoma patients.In pheochromacytoma, hypertension may be either sustained or episodic. The classical hypertensive crisis may arise from a normotensive baseline or may occur in cases of sustained hypertension.In the sustained type of arterial hypertension increased levels of circulating catecholamines can provide a satisfactory aetiological explanation. However, it is less easy to explain hypertensive crisis in terms of current theories such as squeezing of the tumour, or on the basis of cyclic or episodic secretion. 589

Diagnostic Efficacy of Unconjugated Plasma Metanephrines for the Detection of Pheochromocytoma

“…Repetitive blood sampling, however, showed a transient increase of both metanephrine and catecholamine concentrations, even after clipping of the adrenal vein, and a slow decline thereafter ( Figure 3). Release of catecholamines and metanephrines from as yet undefined compartments 17 could explain this phenomenon after the tumor is separated from blood circulation. In addition, the slow decline in the subsequent period suggests continuous production and/or release from storage sites (eg, platelets, endothelium) of plasma catecholamines and metanephrines after clipping of the adrenal vein, not compatible with half-lives of 1 to 2 minutes (catecholamines) and 3 to 5 minutes (metanephrines) reported in clearance studies of these compounds.…”